By THAN HTUN (GEOSCIENCE MYANMAR)
EPISODE:26
ERNEST (WATSON) VREDENBURG
E Vredenburg was born on 17th April 1870 and died in London on 12th March 1923 at the age of 53 years. He was the most senior member of the Geological Survey of India and educated at the Clermont University of France. After working for a short time as an Assistant Chemist in the Creusot Iron Works in France, he joined the Royal College of Science, London, where he took advanced courses in the various branches of Geology. He and Mr. Grimes were appointed Assistant Superintendents in the Geological Survey of India and joined the office in Calcutta, which at that time was situated in the old Museum building, on the 16th of October 1895. Both young officers were sent to Rewah for their camp season under Mr R D Oldham, where the party was greatly handicapped by a phenomenally unhealthy season.
His first official publication in India was a memoir entitled “A Geological Sketch of the Baluchistan Desert and Part of Eastern Persia”, which appeared in 1901; he also, together with Mr P N Datta, assisted Mr R D Oldham in a memoir, which appeared the same year, on the Geology of the Son Valley. Towards the close of 1903, after eight years’ service, he was promoted to the grade of Deputy Superintendent, the initial salary of which post was then R500 per mensem. Early in 1903, he also acted as Curator, and in 1906, was appointed Palaeontologist, a post he filled during the rest of his service. He was again promoted in 1910 to the grade of Superintendent. He returned from leave on 3 November 1912. Placed in charge of the Burma party and left for the field on 8 December 1912. Twice, he performed the duties of lecturer in geology at the Presidency College, Calcutta, and in 1913, he was appointed Calcutta University lecturer in the same subject. His best-known stratigraphical work is that on Baluchistan, which included some intricate mapping. Mr Vredenburg’s energies were, however, devoted chiefly to the subject of Palaeontology, and our knowledge of Indian Tertiary rocks, especially those of Burma, has been clarified and made orderly by much laborious and painstaking work on his part (E H Pascoe, 1923)
According to H H Hayden’s ‘general report of the Geological Survey of India for the year 1913’, Mr Vredenburg spent the greater part of his time at Yenangyaung, where he was permitted to examine in detail the large collections of fossils belonging to the Burma Oil Company. He also visited some of the more important anticlines, the volcanic areas of Popa in the Myingyan district and Shinmadaung in the Pakokku district. Mr Vredenburg’s observations have led him to believe that the fossils described by Dr Noetling in his work on “The Fauna of the Miocene Beds of Burma” (Pal. Ind., New Ser., Vol. I) include two separate faunas, an older and a younger and that these two faunas are separated, one from the other, by an important unconformity extending throughout the Tertiary area in Burma. He believes this unconformity to occur within the Pegu series, dividing it naturally into an upper and a lower, the lower being the chief petroliferous group of beds and the upper being either non-petroliferous or only very sparingly so. So far as Mr Vredenburg’s work has gone, this unconformity is chiefly a palaeontological one, and no conclusive evidence of a general physical or stratigraphical break has been adduced. The hypothesis of the occurrence of this supposed extensive unconformity has not met with general acceptance on the part of other members of the Geological Survey working in Burma, and it would, therefore, be premature to modify at present our classification of the Tertiary system of that province.
Further fieldwork and detailed examination of the extensive collections of fossils made during the last few years by the members of the Burma party will no doubt decide the question. At present, the more generally accepted belief is that the Pegu series, as might be expected in a series of estuarine or shallow-water deposits, contains a large number of small unconformities, none being of very great extent or of more than purely local importance.
Vredenburg has written 51 papers on Palaeontology and of all, the following papers contributed to the Geology of Myanmar. Notes on gem sands from Ceylon and Burma, On the identity of Ostrea promensis Noteling from the Pegu system of Burma and Ostrea digilalina Eichwald from the Miocene of Europe, Results of a revision of some portions of Dr Noteling’s second monograph on the Tertiary fauna of Burma, Illustrated comparative diagnoses of fossil Terebridae from Burma, Comparative diagnoses of Pleurotomidae from the Tertiary formations of Burma, Comparative diagnoses of Conidae and Cancellariidae from the Tertiary formations of Burma, A zone-fossil from Burma: Ampullina (Megatylotus) birmanica, Oligocene Echinoidea collected by Rao Bahadur S Sethu Rama Rau in Burma, Unionidae from the Miocene of Burma and On the Occurrence of Ostrea latimarginata, a characteristic Gaj species, in the “Yenangyaung Stage” of Burma with M Stuart.
Ostrea latimarginata
(Vredenburg)
We are indebted to Mr H J Davies, Geologist to the Burma Oil Company, for one of the most interesting fossils discovered as yet made in Burma. Amongst some fossils sent by Mr Davies from the Pyalo-Kwetha anticline in the Allanmyo subdivision of the Thayet district, there are several shells of an oyster which show the specific characteristics of Ostrea latimarginata, one of the principal zone fossils of the uppermost horizons of the Gáj in Western India.
The Burmese specimens attain yet larger dimensions. In the largest specimens forwarded by Mr Davies, these dimensions are 135 and 130 millimetres, respectively, though the specimen, a lower valve, is fragmentary. When complete, these dimensions must have reached at least 150 mm. In the Burmese specimens, the ribs tend to become obsolete, as in the case of some of the larger specimens from northwestern India. The small number of available specimens from Burma and their indifferent preservation prevent us from ascertaining whether this be a racial character of the Burmese specimens.
According to Mr Davies’s account, the shell must have occurred some 1,500 feet above the base of the “Yenangyaung Stage.” At a lower horizon of the Pyalo-Kwetha section, between 500 and 600 feet above the local base of the “Yenangyaung,” Mr Davies discovered a fauna which he considers to represent the same horizon as Dr Noetling’s zone of Parallelipipedum prototortuosum. The total thickness of fossiliferous marine beds in the section studied by Mr Davies is over 2,200 feet. It is evident, therefore, that somewhere midway through the “Yenangyaung Stage”, there occurs one of the most reliable zones fossils of Western India, and, as it characterizes the uppermost horizon of the Gáj, it confirms Dr Noetling’s surmise as to the Gáj age of the least a considerable portion of the Yenangyaung fauna.
At the same time, it makes it seem more than probable that all the upper subdivisions of Noetling’s “Yenangyoung Stage” are younger than the Gáj of Sind and must correspond in age with the lower zones of the “Hingláj series” of the Mekran province. The bulk of the Gáj strata, abounding as they do with large lepidocyclines, are regarded as Upper Aquitanian. The beds with Ostrea latimarginata and the lower zones of the Hingláj must be ascribed, therefore, to the Burdigalian. (Vredenburg)
Classification of the Pegu system
(M Stuart)
The interesting light that Mr Vredenburg’s determinations have shed upon Mr Davies’ discoveries of molluscan remains amongst the Pegu beds of Pyalo acquires considerable importance, both theoretical and practical, in view of the recent advance lately made in the detailed stratigraphical study of the Miocene of Burma.
With regard to the correlation between “Miocene” and “Pliocene” as formerly applied to the Pegu and Irrawaddy systems, it is barely necessary to point out that these terms cannot be applied any longer, for in view of Mr Vredenburg’s identification, it becomes at once evident that much of the Pegu system is really Oligocene, while all investigations in the Irrawaddy system fail to identify the lowest beds as later than Upper Miocene.
In the area specially studied by Theobald near Prome, the Pegu system includes a considerable thickness of sandstones (the “Prome sandstones” of Theobald’s classification) intercalated between a lower unfossiliferous shale band constituting the Sitsayan shales, and an upper highly fossiliferous shaley horizon known as the Kama clay. The lower 1,400 feet of the sandstones are locally unfossiliferous, or nearly so, while the upper zones are richly fossiliferous.
Noetling in his classification, has altered the use of the name Prome beds, which he has made to include the unfossiliferous Sitsayan shales and the locally unfossiliferous or poorly fossiliferous lower part of the sandstone, while the fossiliferous beds of Theobald’s Prome series have been united with the Kama clays to constitute the Yenangyaung series, thus relying on a purely accidental and local character to split up the well-marked unit constituted by the great sandstone mass.
The discovery of such a characteristic zone fossil as Ostea latimarginata at a definite horizon makes it expedient to return to Theobald’s more natural classification. This form occurs at the upper limit of the Prome beds as originally defined, that is, just below the base of the Kama clay. Since Ostrea latimarginata is particularly characteristic of the upper zones of the Gáj in Western India, we have, by analogy, the Prome series, as originally defined, coinciding with the Gáj and probably an undermined portion of the Nari, while the Kama clay must be equivalent of a portion of the Hingláj beds as defined by Vredenburg.
On the strength of its mammalian fauna, the Irrawaddy system has been regarded as the equivalent of the Siwaliks. Mr. Vredenburg is of the opinion that the newest Hingláj beds are older than Siwaliks proper. It is quite possible that the Irrawaddy system contains representatives both of the Upper Hingláj and of the Siwaliks. The stratigraphical studies so far undertaken are quite insufficient to settle the mutual relations of the beds with marine fossils and those with mammalian remains within the Irrawaddy system. Nor do we know whether any stratigraphical break occurs between mammalian beds and the supposed equivalents of the Upper Hingláj. A distinct unconformity separates the Kama clay from the basement beds of the Irrawaddy system with marine fossils in Lower Burma. Still, the stratigraphical break is not accompanied by any great change in the fauna and may not, therefore, represent a great interval of time.
Nevertheless, the recognition of this unconformity is of great importance in accounting for the extreme divergences in the thickness of the Kama clay, which expands from a foot to more than 1,200 feet in thickness, bringing the succession into closest correspondence with the vast thickness of supra-Gáj clays, mentioned by Mr. Vredenburg. This inconstancy of the Kama clay is a feature that has been brought to light only by the recent survey and was unknown to Dr Noetling. Consequently, the petroliferous beds themselves were referred by Noetling to his Prome stage proper, that is Theobald’s Lower Prome beds and Sitsayan shales, and it has been an accepted idea ever since that those lower beds (Noetling’s Promean) constitute the true petroliferous horizon in the Pegu group.
The detailed studies made in the neighbourhood of another petroliferous locality, Padaukpin, have shown that the petroliferous sands are mere intercalations within the Kama clay, which at that place, in consequence of the irregularities depending upon the above-mentioned unconformity, has expanded to a thickness of considerably more than 1,200 feet. In light of the observations made at Padaukpin and other places, it becomes extremely probable that the petroliferous beds at Yenangyaung are also intercalations in the Kama clay.
In every instance where the petroliferous horizon in the Pegu system can be definitely identified, it is invariably the Kama clays and their subsidiary sandstones that hold the oil, a fact that should be constantly kept in mind in any further search for oil-bearing localities.
References:
1. Hayden, H H 1913: General report of the Geological Survey of India for the year 1913; GSI Record Vol. XLIV, Part 1.
2. Dudly Stamp, L D 1922: An Outline of the Tertiary Geology of Burma; The Geology Magazine Vol. LIX.
3. Pascoe, E H 1923: Ernest (Watson) Vredenburg; Records of the Geological Survey of India Vol. LV.
